Liquid metal transfer switch



April 5, 1966 B. A. OTTERSTEDT 3,244,345

LIQUID METAL TRANSFER SWITCH Filed April 2'7, 1964 FIG. l 10 12 22/ 7 INVENTOR. BROR A. OTTERSTEDT 64 ATTQRNEY United States Patent 3,244,845 LIQUID METAL TRANSFER SWITCH Bror A. Otterstedt, 3535 SW. Spring Garden Road, Portland, Oreg. Filed Apr. 27, 1964, Ser. No. 362,844 5 Claims. (Cl. 200-452) This invention relates to electric switches, and more particularly to a liquid metal transfer switch adapted especially for use in electric circuits carrying high currents, for example in the order of from about 1,000 to over 200,000 amperes.

The present invention represents an improvement over the liquid metal switch disclosed in my U.S. Letters Patent No. 2,990,464, issued under date of June 27, 1961, and entitled, Liquid Metal Switch.

In said Patent No. 2,990,464 there are discussed certain problems arising in the switching of high currents in the electrolytic refining of aluminum. Additional problems have been encountered which have brought about the development of the improvements of the present invention. For example, in the electrolytic refining of aluminum, it frequently occurs that the plurality of electrolytic cells are positioned closely adjacent each other, thus restricting the space between cells to an extent which renders difiicult the placement and operation of my former liquid metal switch. In addition, some electrolytic cells are extremely long, measuring 50 feet or more in length, thus rendering my earlier liquid metal switch somewhat costly, both from the standpoint of the construction of the tanks and of the need for a relatively large volume of liquid metal. Further, particularly in the operation of cells at extremely high current densities, it is desirable that the circuit to the electrodes be broken completely before removal or installation of the electrodes, or other cell maintenance work, is to be accomplished. Still further, it is desirable to provide for the automatic switchingof an electrolytic cell when conditions of operation of the cell become faulty.

Accordingly, it is the principal object of the present invention to provide a liquid metal transfer switch for electrolytic cells and the like, which switch is operable to effect complete breaking of the cell circuit by gradual transfer of current to a bypass circuit without manipulation of any of the components of the cell.

Another important object of this invention is the provision of a liquid metal transfer switch for use with electrolytic cells, which switch accommodates individual adjustment of the cell anodes without the necessity of flexible connectors between the anodes and the switch.

Still another important object of this invention is the provision of a liquid metal transfer switch of compact design, requiring a minimum of space for its installation and operation.

A further important object of the present invention is the provision of a liquid metal transfer switch which requires a minimum amount of liquid metal for its operation.

A further important object of this invention is the provision of a liquid metal transfer switch in which the housing for the liquid metal may be provided conveniently and economically as elongated extrusion of aluminum or other appropriate metal.

A still further important object of this invention is the provision of a liquid metal transfer switch which may be integrated with an electrolytic process, for example, to effect automatic control of the latter.

An additional important object of this invention is the provision of a liquid metal transfer switch of the class described which affords complete freedom on expansion and contraction of the components of adjacent electrolytic cells.

3,244,845 Patented Apr. 5, lfi6 The manner in which the above mentioned objects and other advantages are attained with the present invention, and the construction and operation of the novel switch, will be described with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic View of an electrolytic cell system showing a plurality of cells each having associated therewith a liquid metal transfer switch embodying the features of the present invention;

FIG. 2 is a foreshortened view in side elevation of one of the liquid metal transfer switches shown in FIG. 1, portions being broken away to disclose details of construction; and

FIG. 3 is a vertical sectional view taken along the line 33 in FIG. 2.

Referring first to FIG. 1 of the drawings, there is shown for illustration a plurality of conventional mercury type electrolytic cells 10, 12 and 14. Each cell comprises an elongated enclosed tank defined by upstanding side and end walls, a top wall and a bottom wall.

A secondary bottom wall, spaced above the main bottom wall of each tank, serves to support the mercury cathode 16 above which is contained a quantity of electrolytic solution. A structurally rigid bus bar assembly 18 contacts the mercury cathode, as by connection to a secondary bottom wall made of electrically conductive metal. An assembly of a plurality of anodes 20 is supported within each cell tank, immersed in the electrolytic solution, and is arranged for vertical adjustment as well as for removal from the tank as is well-known. A bus bar assembly 22 is connected to the anode assembly in each cell.

Thus, the electric circuit of each cell extends from the bus bar assembly 18 through the mercury cathode 16 and electrolytic solution, thence through the anode assembly 20 to the bus bar assembly 22.

In accordance with the present invention, a liquid metal transfer switch is provided for releasably connecting a plurality of such cells together in series in a high current electric circuit and for selectively shunting any one or more of the cells to maintain the electric circuit to the remaining cells. It is by this means that any one or more of the cells may be isolated electrically and mechanically for maintenance or repair, without interrupting operation of the remaining cells.

In general, the liquid metal transfer switch of the presentinvention comprises a pair of electrically conductive containers 24 and 26 both adapted to contain electrically conductive metal M in a liquid state. The containers are interconnected by controllable passageway means 28 (FIG. 2) by which to transfer the liquid metal from one container to the other. One of the containers is adapted to receivefreely therein a bypass extension 18' of the bus bar assembly 18 of the cell for immersion in liquid metal when contained therein. The other container is adapted to receive freely therein an extension 22 of the bus bar assembly 22 of the cell for immersion in liquid metal when contained therein. The containers are interconnected electrically for connecting liquid metal in either of the containers to a high current electric circuit.

In the preferred embodiment illustrated in FIG. 3, the liquid metal transfer switch comprises an elongated unitary body made by the extrusion of aluminum or other suitable electrically conductive metal. This extrusion provides vertically spaced upper and lower containers 24 and 26, respectively. The upper container 24 is defined by the spaced side walls 30, 32 and bottom wall 34. The lower container 26 is defined by the spaced side walls 36, 38 and bottom wall 40. The side walls 32 and 38 of the upper and lower containers are joined together by the integral wall extension 42 from which laterally extends the elongated mounting flange 44. The wall extension 42 also serves to space the open upper end of the lower container 26 below the bottom wall 34 of the upper container 24, to provide a lateral passage 46 for the horizontal section 48 of the elongated angular bypass strip. This strip is made of copper or other electrically conductive metal. The associated vertical section 50 of the bypass strip extends vertically downward within the lower container 26 of the switch body, spaced electrically from the walls thereof.

The elongated bypass strip provides the function of the bus bar extension 18 previously mentioned, and is installed in the lower container by slipping it lengthwise through one open-end of the container. The opposite ends of the containers 24 and 26 then are closed by the end plates 52 and 54.

In the arrangement illustrated in FIG. 1, one of the foregoing switches is associated with each electrolytic cell, there being one switch interposed between adjacent cells and an end switch disposed outwardly of the end cell. Thus, the lateral flange 44 of the switch associated with cell is secured firmly, as by welding, to the adjacent end of the structurally rigid bus bar assembly 18 of cell 12. The body of the liquid metal switch thus is supported by the cell 12, in electrical conduction with the mercury cathode of said cell. The switch body preferably extends the full length of the cell. The horizontal section 48 of the bypass strip is secured firmly to the adjacent end of the bus bar assembly 18 of cell 10, whereby the vertical section of the bypass strip is supported in proper position within the lower container 26, spaced from the walls thereof.

In like manner, the switch associated with cell 12 is supported by attachment of its flange 44 to the bus bar assembly 18 of cell 14, and the horizontal section 48 of the bypass strip is secured to the bus bar assembly 18 of cell 12.

The switch associated with the end cell 14 is supported by the mounting of its flange 44 on an insulating base 56. The horizontal section 48 of the bypass strip is supported by the bus bar assembly 18 of cell 14.

A downward extension 22' of each bus bar assembly 22 is adapted to be received freely in the upper container 24 of the associated switch, spaced from the side and bottom walls thereof. In this regard it is important to note that the extension 22 may be secured rigidly to the bus bar assembly 22, i.e. without any interposed flexible connector as is required with conventional mechanical switches, since the extension 22 may move vertically in the container 24 freely as the associated anode 20 is adjusted vertically to compensate for its wear.

In the embodiment illustrated in FIG. 1, one terminal 58 of a source of high current is connected to the bus bar assembly 18 of cell 10, and the other terminal of the supply is connected to the flange 44 of the switch associated with cell 14. The three cells thus are arranged in series in the electric supply circuit.

It will be apparent that as many of the foregoing switch assemblies are utilized as are necessary to interconnect the desired number of electrolytic cells.

The containers 24 and 26 of each switch body are adapted to contain an electrically conductive metal in a liquid state. It will be understood that any electrically conductive metal, or mixtures thereof, capable of being maintained in a liquid state, may be used for this purpose. It is most desirable to use a metal which remains liquid at relatively low temperature. Although mercury may be employed, the precautions necessary to avoid its toxic effects renders its use less desirable than other metals. Among metals and metal mixtures more suitable for this purpose is the mixture having the approximate composition of about 50 parts by weight bismuth, 25 parts by weight lead, 13 parts by weight cadmium and 12 parts by weight tin. This mixture is characterized by having a melting point of 158 F.

Although the foregoing melting point is somewhat above normal atmospheric temperature, it has been found that once it has been liquified by the simple procedure of heating in the containers of the switch body, sufiicient heat is generated during normal operation of the electrolytic cells to maintain the metal in its liquid state. Other metals and combinations thereof may be employed, and some of these may require the use of an external source of heat to maintain the metal in a liquid state.

In the embodiment illustrated in FIG. 3, means for heating the metal in the containers 24 and 26 are provided by elongated electrical heating elements (not shown) contained freely in the bores 62 and 64, respectively, which extend the full length of the switch body.

Passageway means is provided for transferring the liquid metal by gravity from the upper container 24 to the lower container 26. In the embodiment illustrated in FIG. 2, one end of a pipe 79 extends through the end plate 52 to communicate with the bottom of the upper container 24. A second pipe '72 also extends at one end through the end plate 52 to communicate with the bottom of the lower container 26. These pipes are interconnected by a pipe 74 in which a control valve 76 is located for opening and closing the passageway between the containers. Although this valve may be of the manually operated type, it preferably is of the type capable of operation both manually and by electrical solenoid. In this manner the conventional electrical recording or control circuit associated with the operation of the mercury type cell may be utilized to operate the valve to open the passageway when conditions within the cell are detected to be faulty.

Means also is provided for transferring the liquid metal from the lower container 26 back to the upper container 24. In the embodiment illustrated, this means is provided by extending the pipes '76 and 72 from the pipe 74 and connecting the ends thereof to the outlet and inlet, respectively, of a fluid pump 78 driven by an electric motor. Electrically actuated check valves 80 and 82 in the outlet and inlet pipes of the pump are activated to open position upon activation of the pump motor.

The operation of the liquid metal switch of the present invention now will be described by reference to the as sembly of the three electrolytic cells illustrated in FIG. 1. Accordingly, let it first be assumed that liquid metal is contained within the upper containers 24 only of the three switches illustrated. Under this condition it will be seen that the three cells 10, 12 and 14 are connected together in series between the circuit terminals 58 and 60.

Let it now be asumed that it is desired to remove cell 12 from the circuit, for maintenance, repair or other purpose. Accordingly, the liquid metal in the upper container 24 of the switch associated with cell 12 is transferred to the lower container, as illustrated in FIG. 1,.by Opening the valve .76. As the liquid metal flows by gravity from the upper container to the lower container, the extent of immersion of the extension 22 in the liquid metal in the upper container gradually diminishes while the extent of immersion of the bypass section 50 in the liquid metal in the lower container gradually increases. Moreover, substantially maximum liquid metal contact with the bypass section St is eifected before liquid metal contact with the extension 22' is broken, by drainage of liquid metal from the upper container. It is by this means that current transfer from the cell circuit to the bypass circuit is achieved without arcing.

With the liquid metal now contained completely in the lower container 26, the bypass circuit between cells it) and 14 and around cell 12 is formed by the electrical connection of the flange 44 of the switch body associated with cell 10 to the bus bar assembly 18 of cell 12, thence through the bypass strip 48, 5t) and the liquid metal M contained in the lower container of the switch associated with cell 12, thence through the electrically conductive switch body and its lateral flange 44 to the bus bar assembly 18 of cell 14.

The circuit of the anode assembly of cell 12, thus having been completely broken, removal of the assembly now may proceed without hazard or mechanical complication.

After the cell 12 has been readied for insertion back into the series circuit, the liquid metal is transferred back from the lower container 26 to the upper container 24 of the associated switch. This is effected by closing valve 76 and activating the pump 78 (simultaneously activating check valves 80 and 82 to open position).

In returning the liquid metal to the upper container, electrical contact is made first between the liquid metal and the bus bar extension 22', before the liquid "metal contact with the downwardly extending section 50 of the bypass strip is broken. Accordingly, transfer of current back to cell 12 is accomplished without arcing.

By virtue of the use of the same liquid metal in the upper and lower containers of the switch, by transfer therebetween, the required volume of liquid metal is maintained at a minimum. This represents a substantial economy in the practical utilization of the switch, as well be apparent.

Although the previously described integral extrusion of the switch body is preferred, for simplicity and economy, it will be apparent that the body may be constructed by fabrication from strips of copper, steel, or other suitable electrically conductive material. The containers may be offset horizontally, if desired, to facilitate installation and removal of the bypass strip 48. 50.

Various other modifications may be made in the construction which I have illustrated and described, without departing from the principle of my invention, and it is not my intention to restrict my invention otherwise than as set forth in the appended claims.

I claim:

1. A liquid metal switch adapted selectively to connect an electric load in series in an electric circuit and to shunt said load, the switch comprising (a) a pair of electrically conductive containers connected together electrically and adapted for connection to an electric circuit,

(b) electrically conductive metal contained in one of the containers in a liquid state,

(c) passageway means communicating the pair of containers with each other for transferring the liquid metal selectively therebetween, and

(d) valve means in the passageway means for opening and closing the latter,

(e) one of the containers being adapted to receive therein an electrical conductor connecting an electric load in series in the electric circuit when liquid metal is contained in said one container,

(f) the other container being adapted to receive therein a second electrical conductor shunting the electric load when liquid metal is contained in said other container.

2. The switch of claim 1 wherein the pair of containers comprises a unitary switch body of electrically conductive material providing vertically disposed upper and lower containers interconnected electrically.

3. The switch of claim 2 including an electrically conductive bypass conductor in the lower container spaced from the latter and adapted for connection to shunt the electric load when liquid metal is contained in said lower container. 1

4. The switch of claim 2 wherein the passageway means is arranged to accommodate transfer of liquid metal from the upper container to the lower container by gravity.

5. The switch of claim 4 including return passageway means including fluid pump means for returning liquid metal from the lower container to the upper container.

No references cited.

KATHLEEN H. CLAFFY, Primary Examiner. 

1. A LIQUID METAL SWITCH ADAPTED SELECTIVELY TO CONNECT AN ELECTRIC LOAD IN SERIES IN AN ELECTRIC CIRCUIT AND TO SHUNT SAID LOAD, THE SWITCH COMPRISING (A) A PAIR OF ELECTRICALLY CONDUCTIVE CONTAINERS CONNECTED TOGETHER ELECTRICALLY AND ADAPTED FOR CONNECTION TO AN ELECTRIC CIRCUIT, (B) ELECTRICALLY CONDUCTIVE METAL CONTAINED IN ONE OF THE CONTAINERS IN A LIQUID STATE, (C) PASSAGEWAY MEANS COMMUNICATING THE PAIR OF CONTAINERS WITH EACH OTHER FOR TRANSFERRING THE LIQUID METAL SELECTIVELY THEREBETWEEN, AND (D) VALVE MEANS IN THE PASSAGEWAY MEANS FOR OPENING AND CLOSING THE LATTER, (E) ONE OF THE CONTAINERS BEING ADAPTED TO RECEIVE THEREIN AN ELECTRICAL CONDUCTOR CONNECTING AN ELECTRIC LOAD IN SERIES IN THE ELECTRIC CIRCUIT WHEN LIQUID METAL IS CONTAINED IN SAID ONE CONTAINER, (F) THE OTHER CONTAINER BEING ADAPTED TO RECEIVE THEREIN A SECOND ELECTRICAL CONDUCTOR SHUNTING THE ELECTRIC LOAD WHEN LIQUID METAL IS CONTAINED IN SAID OTHER CONTAINER. 